Signs of Fall: Black walnuts

Last night the first ground frost hit Raymore Park. This occurs when the temperature doesn’t go below zero but there is a touch of white on the grass. Hopefully the first air frost is some time away but there are unmistakeable signs of fall, even though most leaves are still green. One sign that is hard to miss is the fruit that seems to be everywhere. From crab apples to acorns, seeds for the next generation are ready to be distributed.

These exotic looking fruit are black walnuts.

These exotic looking fruit are black walnuts.

Black walnut trees are very common in Toronto and provide food for squirrels and the occasional curious human. They are native to Toronto but thrive in cold spots such as Quebec City because they avoid frost damage by leafing late in spring.  The walnuts themselves are surrounded by a fleshy outer skin and then an incredibly hard shell.

This walnut was run over by a car revealing the unbroken inner shell.

The walnut on the left was run over by a car revealing the unbroken inner shell.

Unlike Persian (aka English) walnuts that have been cultivated for millennia, black walnuts are pretty much as nature designed them and as a result are smaller and incrementally more difficult to harvest. Anyone who has attempted to extract a black walnut can only appreciate the skill and determination of squirrels. The trees dispense a natural herbicide called juglone which kills competing plants unlucky enough to be nearby. The toxicity is not isolated to plants; horses should be kept well away from black walnuts. Attempting to extract the nut from the flesh will leave hands turned dark orange by the chemical. The wood is much prized as a veneer.

Thanks to absent-minded squirrels, Raymore Park is a black walnut nursery with more and more planted every year. They grow quickly and can live on average 200 years. As time goes on, walnut trees will increasingly influence the variety of flora and fauna in the park.


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